Tunable cavity



Oct. 20,' 11553 B. B. CORK TUNABLE CAVITY Filed Dec. 27, 1945 grama/Mom BRUCE B. CORK Patented Oct. 20, 1 953 'museum Cavan- Brumm. BeckpMicht,

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morasnartidularlyiftcya tunable resonant cavity adapted' for use with a velocity-modulation tube forggcnerating; on amplifyingghighifrequency-electrical oscillations,

It is an4 object of^ this invention to produce a cavity:tuning means which. operates in a region. niitrimthesicravityw wheremovenenttof thetuning meansiis quite .sensitive im varying. the resonant frequencysfof thacavityt 1f* v ltbis another objectto'thi'ssitilvention@ 'to-prin acavity tuning devieeswhieli is ofsuclpa configuration. that..effectivestuning'j of tlfiwoavity is produced without excessive movement of the tuning device.

In accordance with these objects and with other objects which will become apparent, this invention will now be described with reference to the accompanying drawing in which,

Fig. 1 illustrates in cross section an elevation of the cavity taken along line I-I of Fig. 2, and

Fig. 2 illustrates in cross section a plan of the cavity taken along line 2--2 of Fig. 1.

Referring to the drawing, the cavity is seen to be constructed in the form of a hollow toroid I0, having annular conducting walls II and I2 closed by a conducting peripheral wall I3. An indentation in wall II is formed by circular wall I4 and annular wall I5.

This indentation provides a means for holding L a tube, exemplied in this embodimentas a reflex velocity-modulation tube 20, in the hole of toroid I0. Tube 20 is a conventional type of velocitymodulation tube. The tube comprises an electron gun 2|, resonator grids 22 and23, and a reflector electrode 24. Grids 23 and 22 are connected electrically to annular external terminals 24 and 25, respectively, which are held in contacting relation with walls I5 and I2, respectively, of cavity IIJ, by means of ring holders 30 and 3I. Holders 30 and 3I bear against terminals 24 and 25, respectively, and are held to walls I5 and I2, respectively, by suitable securing means such as screws or bolts.

The structure described thus far will be recognized as av conventional reflex velocity-modulation oscillator comprising principally velocitymodulation tube 20 and specially-shaped resonator cavity IIJ.

The instant invention concerns tuning means for cavity I0, in the form of a pair of conductive segments 40 and 4I, which, placed together, form a ring having an inner diameter slightly larger than the holein the center of the toroid. This Will be clearly seen in Fig. 2 where the two segaclaimsf. (cansa-samecentfer tumori wnereuiefeifeet 1s-mucn mcre pronounced* than elsewhere iir the cavity; segment-sf` 4-U= and? 411 may be moved radi ally-'-v by* means off' theaattaclr'edi noni-conductiverodsf W andl 45, respectively: In* useyit* isf preferablel to.'v

cusly;4 and-'fior this purposeisomeA-formofgangedi tuning* means. fru'rodse-M and 4B* may# becprof vided? f Output from the oscillator is derived thru output loop 5i) feeding a coaxial transmission line 5I.

I n operation, the cavity may be resonated over a continuously. variable frequency band by movement of ring segments 40 and 4I between the position shown in solid lines and the position 46-41, shown in dotted lines. Over the region illustrated, the resonant frequency of the cavity has been found to be very sensitive to the position of ring segments 40 and 4I. This sensitivity is `believed to be due to a combination of two eifects. 'Ihe rst effect concerns the sensitivity of the cavity to capacity loading near its center. as opposed to outer regions of the cavity. The second effect concerns the decrease in capacity between conductive ring segments lll-4I and the opposite wall, encountered at the abrupt points 52 and 53, Where the thickness of the cavity suddenly increases. Therefore, outward movement of ring segments 40-4I not only results in decreased Vcapacitive action, but also removes the capacity from the center of the toroid where its effect is most pronounced.

From the above description, it will be seen that there has been described a tuning means for a cavity, capable of controlling the resonant frequency of the cavity over a continuous and wide range of frequencies without excessive movement of the tuning device.

Although I have shown and described certain specific embodiments of the invention, I am fully aware of the many modifications possible thereof without deviating from the scope of the present invention.

What -is claimed is:

1. A cavity resonator formed by walls made of conductive material, there being an opening in said walls, a thin conductive ring disposed Within said cavity resonator and occupying only a fractional portion of the distance between opposing trally disposed in said walls, a thin conductive ring circumscribing said opening and disposed upon one Wall of said cavity resonator, said conductive ring occupying only a fractional portion of the distance between opposing wall surfaces in the vicinity of said opening, said conductive ring being spl-it into segments, said segments when brought together having an inner boundary slightly larger than said opening, eao'h segment being radially movable to tune said cavity resonator, yand an output loop disposed within said cavity resonator remote from said opening.

3. A cavity resonator for use with an electron beam device comprising walls made of a conductive material forming a cavity, there being an opening in said walls through which said electron beam device is to pass, tuning means comprising moveable segments mounted within said cavity and extending about said opening, said tuning means when brought together having an inner boundary slightly larger than said opening, said segments having a height which is suiciently small so that the enclosed volume of said cavity is not appreciably aiected by said segments, means connected to said segments for moving same relative to each other.

4. A cavity resonator for use with an electron beam device comprising walls made of a conductive material forming a cavity, there being an opening in said walls through which said electron beam device is to pass, the distance between opposing wall surfaces in the vicinity of said opening being substantially less than the distance between opposing wall surfaces from said opening,

tuning means comprising radially moveable Segments mounted Within said cavity and extending about said opening in the vicinity thereof, said tuning means when brought together having an inner boundary slightly larger than said opening, said segments having a height which is suiiiciently small so that the enclosed volume of said cavity is not appreciably affected by said segments, means connected to said segments for moving same relative to each other.

BRUCE B. CORK.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 2,237,873 Haeff Apr. 8, 1941 2,308,523 Llewellyn Jan. 19, 1943 2,353,742 McArthur July 18, 1944 2,391,016 Ginzton et al Dec. 18, 1945 2,410,109 Schelleng Oct. 29, 1946 2,492,155 Kandoian Dec. 27, 1949 

